The proposed research is aimed at identifying (a) the pattern of hemispheric specialization of various cognitive processes (b) as manifested in lateral performance asymmetries in specific tasks and (c) determining how this pattern varies as a function of the simple and interactive effect of individual characteristics. These characteristics, studied in normal college students, are handedness, familial sinistrality, sex, handwriting posture, and sex role identification. Additionally, the effects of corpus callosotomy on hemipheric transfer will be studied in a sample of callosotomy patients. The principal methodology utilized will be reaction time to laterlized visual and auditory stimulus materials. The experiments represent a systematic approach to identifying the effects of individual subject characteristics which modulate cerebral organization. The ultimate result should be to make the effects of hemispheric dysfunction more predictable at the individual person level. The program of studies, meshed with previous results, make possible a differentiated taxonomy of hemispheric specializations for important cognitive processes as a function of readily determinable subject characteristics. One important effect of the program will be to show more conclusively what our previous studies strongly imply--that predictions about hemispheric specialization based on the simple factors of sex, handedness, or familial sinistrality are inadequate and that a more differentiated cerebral organizational pattern is to be discovered by the approach of using more differentiated independent variables (subject characteristics) and tasks that tap more differentiated aspects of language and spatial functions.